Process and apparatus for producing percompounds



Jan. 11, 1938. H. HARTMAN 2,105,438

PROCESS AND APPARATUS FOR PRODUCING PERCOMPOUNDS Filed July 2, 1955 f ATTORNEY H FQJQ Patented Jan. 11, 1938 PROCESS AND APPARATUS FOR monoc- ING PERCOMPOUNDS 'Hermanus Hartman, Roermond, Netherlands, as-

signor to Naamlooze Vennootschap Industrielle Maatschappij Voorheen Noury & Van Der Lande, Deventer, Netherlands, a company of the Netherlands Application July 2, 1935, Serial No. 29,552

In the Netherlands July 6, 1934 7 Claims. (01. 204-9) The present invention relates to process and apparatus for producing chemical compounds by electrolysis. More particularly the invention relates to process and apparatus for producing percreases the resistance to the flow of the electric current through the electrolytic bath.

A further object of the invention is the provision of process and apparatus by the use of 6 salts such as p'ercarbonates and perborates. which greater yields of products, such as per- In carrying outelectrolyses in aqueous solusalts, per unitof electrical energy employed are tion, especially in electrolytically manufacturing obtained. active oxygen containing compounds, such as Referring to the accompanying drawing illuspercarbonates or perborates, the electrolyzers, or trating one embodiment of electrolytic apparatus 10 electrolyte containers; are usually manufactured in which the process of the present invention 10 from acid proof earthenware, vitreous stoneware, may be practiced. sheet iron covered with ebonite, enamelled cast Figure 1 represents a plan or end view of the iron, or other material resistant to the .action of electrolyzer; and Figure 2 represents a section on chemicals. According to the present practice, the line 11-11 of Figure 1, looking in the di- 1 the electrolyzers prepared from thesematerials rection of the arrows. 15 are only partially filled with electrolyte in order In the said views, the numeral I represents a to allow the gases produced during the elecrubber hose through which the electrolyte is trolysis to escape immediately from the elecpumped or caused to flow; and the numerals 2 trolyte. However, this practice of the prior art and 3 indicate respectively anodes and cathodes.

has the disadvantage or inconvenience that'very A plurality of anodes and cathodes are prefer- 20 often compounds or salts resulting from the elecably employed, as shown in the drawing. It is trolysis crystallize out against the walls of the to be understood that the distances between each electrolyzers or between the electrodes, whereby vof the electrodes may be varied, and that the stoppages or short circuits between the electrodes number and arrangement of the electrodes may arise. The objectionable conditions arise most also be varied. The anodes and cathodes maybe 25 frequently when diflicultly soluble compounds or placed in separate rows or circles, or the anodes salts are formed as products of the electrolysis. and cathodes can be arranged alternately in The avoidance of these objectionable conditions rows or circles; and the number of anodes and forms one of the objects of the present invention. cathodes may be'varied in each row or circle.

I have found that the above mentioned draw- In the embodiment of the apparatus illustrated 30 backs are not encountered or do not arise if the in the drawing-six rows of electrodes are shown, electrolyte is pumped through an electrolyzer each row consisting of two cathodes between that is completely filled with the electrolyte to be which is positioned an anode. Each anode 2 is electrolyzed, the walls of the electrolyzer being p e or p d; through the o I along 9- wholly or partly manufactured fr bb r or diameter of the rubber hose I; and two cathodes 35 from another material that does not conduct the 3 pushed or Passed through the hose P electric current find that guarantees a gas tight the side of each anode 2, so that one cathode lies obturationof the electrodes that pass through one slde of anode 2 and another cathode lies on the other side of each anode 2. The conthe walls of the electrolyzer. The electrolytically h bb h 40 1 d ases which are taken along with nections between the walls of t e ru er ose 40 deve ope g I and the anodes and cathodes are gas and liqmoving or pumped electrolyte appear to exercise um tight V eithera mechanical or a physical chemical action The elctrolyzmg chamber which is shown in that prevents the formation of crystals aga nst the drawing as formed of rubber hose, or a the walls of the electrolyzer orbetween the election of rubber hose may have any other m. 45 trodes. able shape or cross section. The electrolyzer Among t e h Objects f the Present inmay also be constructed in such a way that the vention is the provis on of e e rol c DD S wall portions through which the electrodes penein which'the distance between the anodes and trate are manufactured from weak or soft rubcathodes can be made very small, which debar, while the other wall portions are made from 50 a different material, for example iron covered with ebonite, in order to strength the whole thing.

The material for the walls of an electrolyzer according to the invention must. possess the property that it does not conduct the electric current, and those parts in which or through which the electrodes are introduced are advantageously manufactured from a material which possesses sufllcient elasticity to guarantee a gas-tight obturation of the electrodes. Materials such as India rubber, chlorinated rubber, balata and the like meet; such requirements. Preferably the whole elefirplyzer is manufactured from an elastic mateflalilthat does not conduct the electric current, fEexampIe, a soft rubber hose or hose section I, as shown in the drawing, and the electrodes are preferably passed across the electrolyzer so as to be approximately at right angles to the direction of flow of the electrolyte. The electrodes are preferably passed through the electrolyzer so asto be gripped or held at two points. The elastic. material of which the electrolyzer may be formed effectively grips the electrodes in gas and fluid tight relationship when the electrodes are pushed or inserted through the electrolyzer to occupy the positions described above. However, this gas and liquid tight connection may be obtainedln any other suitable manner. I

In practicing the present invention the electrolyzer chamber I may have its axis horizontally or vertically disposed or even inclined to the horizontal. The electrolyte to be electrolyzed may be pumped in at either end. However, when the tube l in the drawing is used with its axis vertically disposed or inclined to the horizontal, it is preferable to pump the liquid upwardly through the tube l as indicated by the arrow shown in Figure 2 of the drawing.

If one passage of the electrolyte through the electrolyzer ,does not accomplish all the electrolytic action or production of compound or salt desired, the electrolyte may be passed repeatedly or continuously through the electrolyzer until the desired amount of electrolytic action in the electrolyte is attained. To this end a pump is caused to withdraw electrolyte to be electrolyzed from a vessel and deliver it to one end of the tube I, whereupon the electrolyte, after being subjected to the action of the electric current in the electrolyzer, is conducted from the other end of the tube I back again to the said vessel, and circulated repeatedly or continuously through the electrolyzer. Interposed between the said vessel and pump may be placed a cooler to bring the temperature of the electrolyte to the desired conditions, or the said vessel may be provided with cooling coils. After the electrolytic action is conducted to the desired extent, the electrolyte may be treated in any suitable manner to separate the products produced. For example, in the production of perborates or percarbonates, these compounds may be separated from the electrolyte by crystallization accompanied .by cooling if necessary.

The gases that are produced during the electrolysis are taken along with the electrolyte, that is pumped around with efllcient rapidity, to prevent the formation 'of crystals against the wall of the electrodes, or between them, in electrolysis in which a diilicultly soluble product or compound is formed, for example, sodiumperborate. It is a surprising feature that the gases taken along, which accordingly have stayed in the electrolyte for some time, do not exercise a detrimental influence on the result of the elec- .trolysis, and that, for example, no reduction of the alkali perborate takes place, owing to the cathodically developed hydrogen, when alkali perborate is produced according to an example hereinafter given.

Example 1 internal diameter of 75 mm. and with a rapidity of 2M per hour. Through the wall of this hose are passed platinum anodes having a diameter of 3 mm. and VzA steel cathodes having a diameter of 3 mm., the distance between the electrodes being 5 to 6 mm. from center to center. VzA steel is a well known product manufactured by Krupp (the well known German works), and its approximate composition is carbon 0.25%, chromium 20%, nickel 7%, the remainder being iron.

At an anodic and cathodic current density of 0.45 ampere per square centimeter and 250 amperes current strength, electrolysis takes place at 10-12 C. and 5-6 volts bath tension.

After leaving the rubber hose, the electrolyte is conducted to a cooling and depositing vessel .in which the sodium perborate formed separates out.

. Example 2 Manufacture of potassium percarbonate.

Water saturated with potassium carbonate is electrolyzed according to Example 1 instead of water saturated with sodium carbonate and borax, except that the electrolysis is preferably conducted at a temperature not over 0 C. The potassium percarbonate is separated by crystallization from the electrolyte.

What is claimed is:

1. Process for preparing a persalt by electrolysis of an aqueous solution which'yields a persalt on electrolysis, which process comprises introducing a flowing stream of the said solution into a chamber having inlet means and outlet means for said solution but which is otherwise closed and which has electrode'means in the path of said solution as it flows fromthe said inlet means to the'said outlet means, said solution in its flow from the said inlet means to the said outlet means entirely filling the said chamber and carrying with it substantially all the products of the electrolysis, and applying a difference of electrical potential to said electrodes for producing the said electrolysis as the solution flows through the said chamber.

2. Process for producing persalts by electrolysis which comprises subjecting an aqueous solution which yields a persalt on electrolysis to electrolysis while it is flowing through an electrolyzing zone, and moving out of the electrolyzing zone, in the flowing solution, substantially all products, including gas, produced as the solution flows through the electrolyzing zone.

3. Apparatus for electrolyzing a solution comprising in combination a tubular chamber, the walls of said chamber being formed of a soft elastic rubber-like non-conductor of electricity, electrodes extending into said chamber through the walls of said chamber and held by said walls in fluid tight connection, means for introducing the solution to be electrolyzed into one end of said tubular chamber, and means for conducting electrolyzed solution away from the other end of said tubular chamber.

4. An electrolyzing cell comprising a tubular chamber, the wall of said chamber being formed of a soft elastic rubber-like material which is a non-conductor of electricity, and electrode means in said chamber extending out of said chamber through said elastic material and in fluid tight relationship therewith.

5. An electrolyzing cell comprising a tubular chamber, the wall of said chamber being formed of a material which is a non-conductor of electricity and having at least a portion thereof formed of a soft elastic rubber-like material which is a non-conductor of electricity, and electrode means in said chamber extending out of said chamber though said elastic material and in fluid tight relationship therewith.

6. Process for preparing a perborate which comprises subjecting an aqueous solution containing a compound of boron, which yields a perborate on electrolysis, to electrolysis while it is flowing through an electrolyzing zone, and moving out of the electrolyzing zone, in the flowing solution, substantially all products, including gas, produced as the solution flows through the electrolyzing zone.

7. Process for preparing a perborate which comprises subjecting an aqueous solution containing a borate, which yields a perborate on electrolysis, to electrolysis while it is flowing through a tubular electrolyzing chamber, and moving out of the electrolyzing chamber, in the flowing solution, substantially all products, in cluding gas, produced as the solution flows through said tubular electrolyzing chamber.

HERMANUS HARTMAN. 

